# All files / src/chap07 HookRef.js

0% Statements 0/11
0% Branches 0/2
0% Functions 0/5
0% Lines 0/9

Press n or j to go to the next uncovered block, b, p or k for the previous block.

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10
    11
    12
    13
    14
    15
    16
    17
    18
    19
    20
    21
    22
    23

     import { useState, useRef } from 'react';

    export default function HookRef() {
      const id = useRef(null);
      const [count, setCount] = useState(0);

      const handleStart = () => {
        if (id.current === null) {
          id.current = setInterval(() => setCount(c => c + 1), 1000);
        }
      };
      const handleEnd = () => {
        clearInterval(id.current);
        id.current = null;
      };
      return (
        <>
          <button onClick={handleStart}>시작</button>
          <button onClick={handleEnd}>종료</button>
          <p>{count}초 경과</p>
        </>
      );
    }